1. Field of the Invention
The present invention generally relates to cable connectors such as balanced transmission cable connectors, and more particularly, to a cable connector such as a balanced transmission cable connector which is suitable for transmitting high speed signals.
2. Description of the Related Art
There are two data transmission methods. One is a normal transmission method and the other is a balanced transmission method. In the normal transmission method, one electric wire is used for every datum. To the contrary, in the balanced transmission method, a pair of electric wires is used for every datum. A “+” signal and a “−” signal are simultaneously transmitted in the balanced transmission method. The magnitude of the “−” signal is equal to that of the “+” signal. The direction of the “−” signal is reverse to that of the “+” signal. Use of the balanced transmission method is on the increase for data transmission because the balanced transmission method has an advantage in that it is more robust against noise than the normal transmission method. A balanced transmission cable connector has a structure where a plug is provided at an end of a balanced transmission cable and the plug is covered with a shield cover. The balanced transmission cable connector is applied to the balanced transmission method and used for connecting a computer and a server.
FIG. 1 is an exploded perspective view of a related art balanced transmission cable connector 10. FIG. 2 is a cross-sectional view of the balanced transmission cable connector 10 shown in FIG. 1. In FIG. 1 and FIG. 2, a direction of X1–X2 shows a width direction of the balanced transmission cable connector 10. A direction of Y1–Y2 shows a longitudinal direction of the balanced transmission cable connector 10. A direction of Z1–Z2 shows a height direction of the balanced transmission cable connector 10. A direction of Y1 shows a rear direction and a direction of Y2 shows a front direction. FIG. 3 is a cross-sectional view of a related art balanced transmission cable 20. The balanced transmission cable connector 10 is connected to an end part of the balanced transmission cable 20 having a structure shown in FIG. 3-(A) and FIG. 3-(B).
As shown in FIG. 3-(A), the balanced transmission cable 20 has a structure where a lot of pair electric wires 21 are arranged inside of a tube which has a double covering structure formed by a tube-shaped electrically insulating outer covering part 27 and a shielding mesh 28. As shown in FIG. 3-(B), each of the pair electric wires 21 has a structure where a pair of first and second covered signal electric wires 22-1 and 22-2 and a drain wire 26 are wound in a spiral form by a metal tape 25 so as to be bound. The first and second covered signal electric wires 22-1 and 22-2 and the drain wire 26 are extended from an end part of the pair electric wire 21 to the outside. Head end parts of the first and second covered signal electric wires 22-1 and 22-2 are processed so that first and second signal wires 23-1 and 23-2, respectively, are exposed in a naked state. The first and second covered signal electric wires 22-1 and 22-2 include electrically insulating covering parts 24-1 and 24-2, respectively. The first and second covered signal electric wires 22-1 and 22-2 form a pair wire. In addition, as shown in FIG. 2, an end part of the balanced transmission cable 20 is clamped by a clamp member 27.
Referring back to FIG. 1 and FIG. 2, a relay board 12 is fixed to a Y1 side of a plug assembly 11. The pair electric wires 21 provided at the end part of the balanced transmission cable 20 are arranged in X directions by an electric wire arranging member 15. The first and second covering signal electric wires 23-1 and 23-2 and the drain wire 26, which are further extended from the ends of the pair electric wires 21, are solder-connected to a terminal part situated at the Y1 side of the relay board 12, as shown by a numerical reference 14. Shield covers 31 and 32 cover the plug assembly 11, the relay board 12 and the electric wire arranging member 15. The shield covers 31 and 32 are engaged with the clamp member 27. The plug assembly 11 and the clamp member 27 limit movement in the Y1 direction. A synthetic resin part 16 is a part where synthetic resin in a molten state is solidified after a signal wire or the like is soldered. The synthetic resin part 16 covers a part where the first and second covering signal electric wires 23-1 and 23-2 and the drain wire 26 are soldered and connected to the terminal part at the Y1 side of the relay board 12, so that a solder connecting part 14 is reinforced. See Japanese Laid-Open Patent Application No. 2003-59593.
In the balanced transmission cable connector 10, the clamp member 27 is fixed to the shield covers 31 and 32. The balanced transmission cable connector 10 has a structure where even if the balanced transmission cable connector 10 is inserted into or pulled out from a socket of the computer so that the balanced transmission cable 20 is curved, there is no influence of the curve to an inside of the balanced transmission cable connector 10, more specifically to the solder connecting part 14.
However, the pair electric wires 21 are bound by a tube and therefore not fixed to each other. Accordingly, in a case where, for example, a clamp force by the clamp member 27 is not sufficient, if the balanced transmission cable 20 is pulled and curved, a pulling force of a certain pair electric wire 21 is transferred to even the inside of the balanced transmission cable connector 10 via the clamp member 27.
The synthetic resin part 16 is situated on only the upper surface and the lower surface of the relay board 12. Therefore, the pulling force transferred via the clamp member 27 reaches to the solder connecting part 14 covered by the synthetic resin part 16, via the electric wire arranging member 15. As a result of this, a stress is applied to the solder connecting part 14.